Conversion of hydrocarbons



June 5, 1944 E. E. sl-:Nsl-:L ET Al.

CONVERSION OF HYDROCARBONS Filed June 18, 1941 wumdw 2 Patented June A6,1944 CONVERSION F HYDROARBONS Eugene E. sensei and Arthur a. Goldsby,Beacon, N. Y.. assixnors. by mesne assisnments. to The Texas tion ofDelaware y Company, New York, N. Y., a corpora- Appueaaon :une 1s,1941,- smal No. a9s,5ai v 4 claims. v(ci. 26osaam This invention relatesto the conversion of hydrocarbons and has to do with the isomerizationoi' hydrocarbons to form branched chain hydrocarbons and particularlyhas to do with the isomerization of saturated gasoline hydrocarbons.

'Ihe invention broadly contemplates treating a mixture of gasolinehydrocarbons, including aliphatic and alicyclic hydrocarbons, to removealicyclic and other objectionable constituents which tend to' causecatalyst deterioration during isomerization, and thereaftersubjectingthe gasoline hydrocarbons to isomerization in the substantialabsence of alicyclic and other objectionable constituents whereby theisomerization reaction is effected at relatively low temperature toobtain substantial conversion of the paramn constituents toisoparafllns.

Gasoline or naphtha usually comprises a mi-xl ture of saturated andunsaturated hydrocarbons. The saturated hydrocarbon constituentscomprise paramns and saturated naphthene hydrocarbons, while theunsaturated constituents comprise oleflns including cyclo-olefins. Inaddition, aromatic hydrocarbons may be present, particularly if thehydrocarbon mixture is a cracked naphtha.

Aromatic and -unsaturated hydrocarbons readily react with anisomerization catalyst such as an active metallic halide catalyst toform complexes or sludge thereby causing substantial catalystdeterioration. Consequently, it has been found desirable'to removearomatic and unsaturated hydrocarbons from thefeed to an isomerlzationreaction.

The present invention has to do with the removal of both saturated andunsaturated alicyclic hydrocarbons from the feed to the isomerizationreaction and particularly where it is desired to carry out the reactionat relatively low temperatures. At relatively high temperatures thepresence of saturated ialicyclic hydrocarbons, namely naphthenehydrocarbons, appears to impart a benecial action. Thus, as disclosed incopending application, Serial No. 398,530 lled June 18, 1941, forConversion of hydrocarbons, where the isomerization reaction is carriedout under temperatures, for example; in the range 160 F. and above, inorder to obtain high yields of isoparamns it is desirable to effect thereaction in the presence of substantial amounts of naphthenehydrocarbons for the purpose of inhibiting cracking and side reactionswhich would'other- :vise occur at these relatively higher temperaures. t

However, the present invention has to do with the discovery that in thelow temperature isomerization o1' gasoline or naphtha, it isadvantageous to remove naphthene hydrocarbons from the feed and thuseii'ect the isomerization reaction in the substantial absence of suchhydrocarbons as well as in the substantial absence of aromatic andoleiinic hydrocarbons. In other words, for a low temperature operation,it is advantageous to select a feed stock which is essentially free fromnaphthenes.

For, example, when isomerizing gasoline hvydrocarbons in the substantialabsence of naphthene hydrocarbons so as to obtain about 30 to 40%conversion of normal parans to isoparaffins it has been found/that thereaction temperature can be maintained at least about 25 F. and in somecases as much as F.'or more, lower than the reaction temperaturerequired where the feed contains naphthenes in substantial amount.

In practice the temperature of reaction may range from about 100 to 200F., although the particular temperature employed will depend upon thenature of the catalyst. and the specic manner in which the reaction iscarried out. It

will also depend upon the nature of the paramn feed to the reaction.'I'hus when the feed con-- sists essentially of normal pentane vand there` action is eli'ected with anhydrous aluminum chloride promoted withanhydrous hydrogen chloride but in the substantial absence. ofextraneous agents such as isobutane, the temperature may be about 100 to130 F. for example.

The following conversion yields aord a comparison of the resultsobtained in the low temperature isomerization of normal pentane .withaluminum chloride and hydrogen chloride; first in the absence ofcyclohexane and, second, in the presence of cyclohexane, the naphthenebeing present in the latter case to the extent of about 25% by weightofthe pentane feed to the reaction. The data were obtained in batchliquid phase experiments carried out at temperatures of 100, 130, and200 F. witha reaction time in each case of 4 hours. In each experitpowdered anhydrous aluminum chloride of 200 mesh was charged to areaction vessel extent of by weight of the feed hydrocarbon, thereaction. being promoted by the addition of about 0.5 to 0.7% 'ofhydrogen chloride by weight of theyfeed hydrocarbon.

temper-aimes up to 130 and somewhat above, the

conversion -of normal pentane to isopentane and other hydrocarbons issubstantially greater in the absence of the naphthene hydrocarbon. Infact there is little orfno conversion in this temperature range in thepresence of the naphthene. Moreover. in the lower portion ofthe reactiontemperature rance. for example, in the range 100 to Labout 120 1".. theconversion product' obtained in the absence of the naphthene consistsessentially of isoparaiiin. i. e., isopentane. However. at temperaturesof 130 Il'. and above where thereactionia carrledoutinthe absence of thenaphthene hydrocarbon. the content of isopentane in the reaction productis proportionately less. falling oi! rather markedly at temperatures inthe neighborhood of 100 F. due to cracking and side reactions with. theformation of products other than isopentane.

\ As previously explained naphtha or other mixinra of gasolinehydrocarbons substantial amounts of naphthene hydrocarbons, In someinstances, feed stocks may be selected from which an isomeriaation feedsubstantially free from naphthene constituents may be obtained byconventional methods of fractional disdistillation, extraction withsolvents or by other methods.

l'br example, the hydrocarbon mixture containing naphthene constituentsmay be subjected to contact with a suitable dehydrogenation catalystauch as chromium oxide or molybdenumoaideadvantageouslydisposedupon a.

mpporting material such as alumina. and the contact effected undersuitable conditions of temmay becontinuously recycled through thereaction zone.

For example, the reaction may be carried out employing a space velocityof about 0.5 to 1.0 (volumesof liquid feed measured at 60 F. per volumeof catalyst). 'The light gases produced in the reaction and rich inhydrogen may be recycled at the rate of about 2500 cubic feet of gas perbarrel of hydrocarbon feed to the reaction where the feed is a virginnaphtha, and may be as high as 10,000 cubic feet where the feed is acracked naphtha.

If desired the products `of reaction of the'hydroformlng reaction may besubjected to a hydroiining action in which the hydroformed products arepassed to a separate reaction zone containing a hydroforming catalystand maintained at a somewhat lower temperature so that the olefinicconstituents are subjected to hydrogenation. V f

The catalytically converted naphtha resulting from the foregoingoperationswill comprise paramn, aromatic and oleflnic constituents, the

naphthene constituents originally present in the a initial feed havingbeen converted to aromatic and other constituents as a result of thereaction.

After fractionation to remove normally gaseous constituents and alsoheavier hydrocarbons boiling above the motor fuel range the convertedgasoline is subjected to a conventional extraction with a solventsuch asliquid sulfur dioxide,

usually contain Vsventureaailpressuresoastoob'tainthe@Stilisti ,75

dichloroethyl ether, furfural, nitrobenzene, etc., to effect aseparation into extract and raillnate phases. The raillnate phasecomprises paraffin hydrocarbons substantially free from naphthene,aromatic and unsaturated hydrocarbons while the extract phase comprisesaromatic and unsaturated hydrocarbons. 'Ihe extract phase after removalof the solvent will thus comprise gasoline hydrocarbons having arelatively high octane number, for example, about 80 to 100 andtherefore, suitable as a blending stock for motor fuel. y

The rainate after removal of the solvent is then subjected to contact,with an isomerization catalyst at a relatively low temperature in orderto convert the paraffin constituents to isoparaiiln hydrocarbons,thereby producing a mixture of gasoline 'hydrocarbons of high antiknockvalue.

The foregoing fractionation and solvent extraction operations may bemodified to make provision for segregating from the converted naphtha atoluene fraction or concentrate where it is desired to segregate thetoluene for some particularpurpose. l

If desired, the raillnate, prior to isomerization, may be subjected to afurther chemical treatment in order to remove any remaining smallquantities of aromatic and olefin constituents. Por example, theraiilnate, after removal of the solvent. may be subjected to treatmentwith sulfuric acid followed by neutralization with caus- .Theisomerization reaction may also be cartic or other suitable alkalinematerial.

The accompanying `drailvingcomprises a flow diagram illustratingmnemethod of Vcarrying-out the reaction.l Thus, referring to the drawing, a

The resulting reaction mixture is conducted through a pipe I to afractionator l wherein fixed or normally gaseous constituents areremoved as a gaseous fraction from the topof the fractionator whilelhydrocarbons boiling above the motor fuel rangeare removed as a residualfraction from' the bottom of the fractionator.

As previously mentioned, in the case of a hydroforming reaction thegaseous fraction or any portion thereof rich in hydrogen removed fromthe top of the i'ractionator l may be recycled to the reactor 2.

A side stream comprising hydrocarbons of motor fiel boiling range isdrawn off from the 4fractionator through a pipe 5. This side stream willcomprise parailin hydrocarbons together with unsaturated hydrocarbonsand aromatic hydrocarbons including aromatic compounds formed as aresult of the conversion of naphthenes in the reactor 2. This stream isconducted to an extractor 8 wherein it is subjected to extraction with aselective solvent such as already mentioned.

I'he resulting railinate phase is drawn off through a pipe 'Iv to astripper 8 wherein the solvent is stripped from the ralnatehydrocarbons, the solvent being recovered for reuse.

The solvent free raiiinateV through a pipe 9 to a chemical treatingplant III wherein it is subjected to conventional acid and caustic'treatments to remove any remaining traces of aromatic and unsaturatedhydrocarbons.

is conducted The treated raffinate thereafter is lconducted through apipe Il to a reactor I2. A5 indicated in the drawing the chemicaltreating stepmay be bypassed in which case the ramnate is conpipe I3ydirectly toV the reactor chloride and in which case the reaction islcarried out at a temperature in the range about 100 to notin excess ofabout 130 F. Temperatures as low as 50 F. maybe used, and temperatureshigher than 130 F. may be used provided the reaction is carried outunder conditions such that cracking and side reactions. are avoided. Thetemperature will depend upon the feed hydrocarbon, that is, highertemperatures maybe permissible with some stocks even though naphthenehydrocarbons are absent. Other metallic halides may be employed as, forexample, aluminum bromide.- Other hydrogen halides may be employed suchas hydrogen bromide.

ried out in either the gas or liquid phase, employing the catalyst inthe form j of' a massof solid particles or lumps, `or in the form o f afiu'id mixture of vpowdered catalyst dissolved or suspended in a'iiquidmedium such as metallic halide-hydrocarbon complex. 'I'he reaction maybe carried out with finely divided solid catalyst suspended linvaporized hydrocarbons undergoing conversion.

In any case the iscmerized hydrocarbon mixture is" conducted through apipe I 4 to Ya fractionator Il. In the fractionating .step gaseoushydrocarbons tending toaccumulat'e v-in the reaction are removed througha pipe I6. These gases will comprise normally gaseous hydrocarbons suchas normal butane and isobutane and some hydrogen as well as hydrogenchloride. If desired, a suitable proportion of the gaseous hydrocarbonssuch as isobutane or the hydrogen as well as the hydrogen chloride maybe continuously recycled through the isomerization reactions zone forthe purpose of facilitating the reaction and inhibiting the occurrenceof cracking and side reactions.

High boiling hydrocarbons are drawn off from the bottom of thefractionator through a pipe I1, While a side stream including isomerizedhydrocarbons boiling within the desired motor fuel Vboiling range isdrawn oil' through a pipe I8. y

Referring again to the extractor 6, the extract phase isidrawn offthrough a pipe 20 and conducted to a stripper 2| wherein the solvent isrecovered for reuse. 'I'he solvent free extract comprising aromatic andunsaturated hydrocarbons is drawn oil. through pipe 22 and may besubjected to further treatment for the purpose of stabilizing colorandgum. forming constituents. The extract hydrocarbons, as alreadyindicated, comprise valuable gasoline hydrocarbons of relatively highoctane number and this material is advantageously conducted all or -inpart through a pipe 2 3 to a tank 24 wherein itis blended in suitableproportion with the-isomerized hydrocarbon mixturedrawnofi' through pipeI8.

The arrangement of apparatus indicated in the drawing is merelydiagrammatic and it is contemplated that in`actua1 practice rthearrangement of apparatus as well as the method of flow may be varied.For example, the dehydrogenation or hydroforming reactions and also theisomerization reaction may be carried out in a batch or continuous: typeof operation employing single or multistage reactors with provision formultiple injection of the feed and/or promoter to the re. action zone orzones. j The catalytic reactions may be carried out so as to permiteither continuous concurrentor countercurrent flow of hydrocarbonsundergoing treatment and a stream of catalyst in a reaction zone orzones. l

An `advantageous mode of carrying out the isomerization reactioninvolves the employment of a fluid type of operation wherein asubstantial body of fluid containing ythe catalyst dissolved orsuspended therein is maintained in al reaction zone with provision forcontinuous withdrawal of a stream of the reaction mixture and continuousrecycling of the withdrawn stream to thefreaction zone. Suillcient ofthe liquidmixture is recycled to impart thorough agitationto thereaction mixture within the reaction zone. If desired the paraflln feedmay be introduced to the reaction zone Ain the form `of a large numberof separate streamssimultaneously to the mass of reaction 4 l assenteLikewise the fractionating apparatus may be 5 modified so as to effectany desired degree or type of fractionation at dierent stages in theprocess.

l In the above described experiments a reaction of 4 hours is used.However, it is contemplated that a reaction time of 1 hour or less maybe employed. For example, in continuous operations the reaction time maybe about 5 to 15 minutes and as high as 2 hours or more.

Obviously many modifications and variations While specific examples ofdehydrogenatlng of the invention, as hereinbeiore set forth, may andhydroiorming catalysts have been mentioned, be made without departingfrom the spirit and it is intended that other catalysts maybe em- Ascope thereof, and therefore only such limitations ployed for thispurpose. Additional examples oi .I dehydrogenating catalysts which maybe employed are metals such as silver, copper, iron, nickel, cobalt,aluminum, or alloys thereof, or

sulildes or oxides of iron, nickel, cobalt, zinc, cadmium, aluminum,lead, bismuth, tin, vanadium etc. Particularly effective catalystsconsist of, or contain oxides or sulfldes of the metals of tire 6thgroup of the periodic system, namely, chromium, molybdenum, tungsten,uranium, selenium,

tellurium and polonium. The catalysts may be used alone or in admixturewith each other for deposited on solid carriers. Suitable carrierscomprise silica, silicates, carbon, charcoal, etc".

Examples of hydroforming catalysts include,-

oxides of aluminum, boron, silicon, titanium, tin,

molybdenum, selenium, tellurium, etc., also activated earths and clays,etc.

Also, if desired, the feed mixture prior to introduction to the reactor2 may be subjected to 30 lytic conversion carried out in the reactor 2may 3 be utilized to effect removal of sulfur and other impurities to asubstantial extent. The removal of such impurities-from the feed to theisomerization reaction is desirable from the standpoint of preventingcatalyst deterioration. j

thereof may be subjected to further refining or processing as desired.For example, the isomerized hydrocarbons together with promoter.rremoved from the fractionator I 5 may be passed 45 directly to analkylation unit wherein theiisoparaiiin hydrocarbons are caused to reactwith olefin hydrocarbons by contact with a metallic halide catalystmaintained under alkylating conditions. For example, an isopentanefraction-of the isomerized hydrocarbons together with hydrogen chloridepromoter may be passed to a suitable alkylation operation for reactionwith an olefin such as triisobutylene in the presence of aluminumchloride catalyst to produce safety` neous gases including hydrogentothe feed to the isomerization reaction.

The hydrogen from the dehydrogenation reaction may advantageously beused in the isomerization reaction to decrease' catalysi-consumption andenable higher conversions to bel obtained without substantial cracking.

should be imposed as are indicated in the appended claims.

We claim:

1. The method of isomerizing gasoline hydrocarbons present in mixturesof straight chain and cycloparamn hydrocarbons by the action of anisomerization catalyst selected from the group consisting of aluminumchloride and aluminum lbromide in the presence of hydrogen halidepromoter at relatively low temperatures, which comprises removing fromthe feed mixture at least a substantial portion of the cycloparaiiinconstituents present therein, and then subjecting residual straightchain parailin constituents to contact with the catalyst underisomerizing conditions in the substantial absence of said cycloparafllnconstituents and at a temperature in the range F. to substantially below160 F. such that the weight ratio of isoparafiin produced to normalparamn converted is not substantially less than .77 and such thatconversion of normal paramn constituents to isoparamns is substantiallygreater than that obtained under substantially similar conditions ofreaction in the presence of said removed cycloparailln hydrocarbons.

2. The method of isomerizing gasoline hydrocarbons present in mixturesof straight chain and cycloparamn hydrocarbons by the action of anisomerization catalyst selected from the group 40 consisting of aluminumchloride and aluminum The isomerized hydrocarbons or any portion bromidein the presence of hydrogen halide p romoter at relatively lowtemperatures, which comprises removing from the feed mixture at least asubstantial portion of the cycloparaiin constituents present therein,and then subjecting residual straight chain paraflin constituents tocontact with the catalyst under isomerizing conditions in thesubstantial absence of said cycloparaflln constituents and at atemperature in the range about 100 to 130 F. suchthat the conversion ofnormal parailin constituents to isoparaillns is substantially greaterthan that obtained under substantially similar conditions of reaction inthe `presence of said removed cycloparailln hydrocarbons. l e

3. The method of isomerizing gasoline hydrocarbons present in mixturesof straight chain and cycloparailln hydrocarbons by the action of anisomerization catalyst selected from the group consisting of aluminumchloride and aluminum bromide in the presence of hydrogen halidepromoter at relatively low temperatures, which comprises obtaining asaturated gasoline fraction comprising straight chain andcycloparaiilnshy- 5 drocarbons having from 5 to 7 carbon atoms permolecule, removing from said fraction substantially all of thecycloparamn constituents present therein, and then subjecting residualstraight chain paraflln constituents to contact with the catalyst underisomerizing conditions in the substantial absence of said cycloparaiiinconstituents and at a temperature in the` range about 100 to F. suchthat the conversion of normal parafiin constituents to isoparafllns issubstantially greater than obtained under substantially similarconditions of reaction in the presence of said removed cycloparamnhydrocarbons.

4. The method of isomerizig gasoline hydrocarbons present in mixtures ofstraight chain and cycloparamn hydrocarbons by the action of anisomerization catalyst selected from the group consisting of aluminumchloride and aluminum bromide in the presence of hydrogen halidepromoter at relatively low temperatures, which comprises removing tromthe feed mixture at least a substantial portion oi' the cycloparamnconstituents present therein. and then subjecting residual straightchain paramn constituents to contact with the catalyst under isomerizingconditions in the substantial absence of said cycloparailln constituentsat a temperature in the range not substantially above 130 F. such thatconversion oi normal parafiln constituents to isoparamns issubstantially greater than that obtained under substantially similarconditions of reaction in the presence of said removed cyclo- 10 paramnhydrocarbons.

EGENE E. SENSEL. ARTHUR GOLDSBY.

